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Hi I like to build a laser pointer that reflects different shapes for a project I am working on. I know this can be done with Diffractive Optical Elements. Are there other options? DOEs are expensive.

I see all these laser pointers with different shapes (arrow, hand etc), I am suspecting there is a lower cost but lower performance way. Any pointers?

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This forum is going to become "Advice in any situation" chat. Vote to close. One can buy really cheap laser pointers with alot of DOEs included! –  Georg Aug 4 '11 at 12:41
    
"Building oneself" is often using a 5 mW or more dangerous laser! –  Georg Aug 4 '11 at 12:51
    
We could use a tag for tinkering with experimental equipment and similar "make it" projects, but I haven't been able to frame one I like. –  dmckee Aug 5 '11 at 0:40

2 Answers 2

up vote 9 down vote accepted

It is possible to do diffractive optics really cheap - either with photography (with a non-digital camera) or a widely available DTP polygraphic technique. What you need is to:

  • Make a Fourier transform of an image you want to have (it should be relatively simple).
  • Make an image which is white when the real part of the FT is positive, and black - when it is negative.
  • Either print it, make a photo with a classical camera, develop the film and use it as you diffractive device OR prepare a pdf/ps file and go to a DTP point (resolution up to 5000dpi should be possible; a few $ per A4 sheet on which you can make a lot of patterns).

As it uses absorption, not refraction, so some loss of intensity is unavoidable.

Some patterns can be found here (mainly: Fresnel zone plates and diffractive gratings) http://migdal.wikidot.com/en:spz-moire-ps

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Cool. Could you give a link two such a polygraphic DTP shop? It's hard to google there are too many lie detectors. –  whoplisp Aug 4 '11 at 15:54
    
Try the following keywords : DTP studio, polygraphy, digital print(ing), offset print(ing) + your town/city. Or just DTP or offset in Google Maps or another map/service search. Some services are related to advertising agencies or printing/xerox points. At least in Warsaw there is abundance of it. –  Piotr Migdal Aug 4 '11 at 17:01
    
beautiful answer.. I will try it.. Is there a tool where I can generate an FFT of an image with ease? –  Frank Aug 5 '11 at 5:56
    
Any programming language with mathematics. E.g. Python astrobetter.com/fourier-transforms-of-images-in-python (though I never used it for that purpose). Keep in mind you need to have diffractive pattern which is same/smaller than size diameter of your beam. –  Piotr Migdal Aug 5 '11 at 12:38

One option would be to expose a hologram into photographic film (or ideally a photographic plate).

I also heard of people who wrote holograms into (or onto) plastic but I'm not sure if you need pulsed lasers to write those holograms.

A cool solution is to use a phase-only spatial light modulator, e.g. by Hamamatsu. The Hamamatsu device costs probably 5000 EUR but possibly you can use a normal LCD screen after you removed the polarizer foils.

The coolest solution (in my opinion) is to build an acousto optic deflector. There you use an ultrasound transducer to create a thick grating within some transparent crystal (but I think glass works as well). The laser light will be deflected. You can vary the angle of deflection by changing the frequency of the ultrasound. You can put two of these things behind each other. Then you can scan the beam in XY (like an oscilloscope). Note that this isn't really shaping the beam. But you can scan the beam very fast.

I always wondered if one could write a hologram on a DVD or Blue-Ray medium. If one understands the burners firmware good enough to put the data into specific places this might actually work. And 50Gb of information would make for some pretty detailed pictures.

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The cheapest way to produce holograms is making a metal "stamp" (technology like CDs or vinyl records are/were made) and use that to mould plastic, or just press it onto a plastic foil. Price is then a question of copies sold. Copys of optical grids were made more than 100 years ago by casting a collodion solution on the grid and peel it off after drying. –  Georg Aug 4 '11 at 14:49
    
Why the down vote? –  whoplisp Aug 4 '11 at 15:57
1  
@Georg: see dx.doi.org/10.1117/1.1598209 and dx.doi.org/10.1117/12.526504 . I have access only to the first one and it seems that some hardware modification of the CD-writer is required. –  Piotr Migdal Aug 4 '11 at 17:16

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